Fire-resistant glass containing a gel with improved melting resistance, and process for the preparation thereof

ABSTRACT

Fire-resistant glass, produced by placing between two panes of glass a gel former containing a) an acid aluminum phosphate, b) a reaction product of boric acid with an alkanolamine and one or more alkali metal compounds, and heating the glass to convert the gel former to a gel.

This application is a divisional of application Ser. No. 08/587,197,filed on Jan. 5, 1996, now U.S. Pat. No. 5,709,821.

EP-A 1 596 324 describes gel formers and EP-A 1 596 322 describesfire-resistant glass containing gels obtained from such gel formers,with the gel formers being characterized in that they contain a) acidaluminium phosphates, optionally in the form of reaction products withfrom 0.01 to 4 mol of alkanolamine per mole of aluminium phosphate andb) reaction products of boric acid with alkanolamines, with a) and b),calculated as solids, being present in a weight ratio of from 100:50 to100:0.5. Preference is here given to gel formers containing from about0.5 to 85% by weight of water and aluminium, boron, phosphorus andalkanolamine in atomic or molar ratios of 1:1.2-1.8:2.3-3.7:2.3-3.7. Inaddition to aluminium compounds, up to 20 mol %, based on aluminium, ofmetal compounds can be used, e.g. those from the first main group of thePeriodic Table of the Elements. This corresponds to an atom ratio ofaluminium to additional metal of 1:0.0-0.2.

These known gel formers have pH values in the range from 5 to 6 andrequire gelling times of from 3 to 80 hours at from 45° to 120° C.,preferably from 10 to 40 hours at from 60° to 95° C.

It has been found that these known gel formers are not fullysatisfactory in respect of their temperature resistance and adhesion toglass. Additions of alkali metal hydroxides in the range up to 20 mol %(based on aluminium) lead to considerable lengthening of the alreadylong gelling times (see Example 2, sample B).

In addition, it has been found that for the application infire-resistant glass an intermediate intumescence capability of the getsis better than a very high intumescence capability, since if excessivefoaming occurs in case of fire, there is a danger of premature breakingof fire-resistant glazing. In the case of the known gels, such apremature breaking can not always be ruled out.

In the range from 300° to 500° C., the known gels have a good meltingresistance. However, at lower temperatures undesired melting can occurwhich can lead to a premature flowing away of the gel if in the case offire higher temperatures occur at the fire-resistant glass only after arelatively long time.

The present invention provides gel formers containing

a) acid aluminium phosphates, optionally in the form of reactionproducts with from 0.01 to 4 mol of alkanolamine per mole of aluminiumphosphate and

b) reaction products of boric acid with alkanolamines,

which are characterized in that a) and b), calculated as solids, arepresent in a weight ratio of from 100:95 to 100:0.5 and that theyadditionally contain alkali metal compounds in an atom ratio ofaluminium to alkali metal of 1:1.3-2.5.

The gel formers of the invention preferably contain from 0.5 to 85, inparticular 10 from 20 to 50, % by weight of water.

Furthermore, preference is given to gel formers containing aluminium,boron, phosphorus, alkanolamine and alkali metal in atomic or molarratios of 1:1.2-1.8:2.7-3.3:2.7-3.3:1.4-2.2.

The reaction components used for the preparation of gels according tothe invention are preferably aluminium hydroxide, orthophosphoric acid,orthoboric acid, monoethanolamine and alkali metal hydroxide.

Gel formers according to the invention can be prepared, for example, byfirst preparing a get former corresponding to EP-A 1 596 324(hereinafter also referred to as preproduct) and adding the alkali metalcompound in the desired amount to this at from 10° to 100° C. Thispreparation is preferably carried out at from 20° to 60° C., with goodstirring and using from 50 to 70, in particular from 30 to 55, %strength by weight aqueous solutions of the alkali metal compounds.

Fire-resistant gels according to the invention are gel formers accordingto the invention in gelled form. Fire-resistant gels according to theinvention can be prepared, for example, by heating gel formers accordingto the invention to from 50° to 120° C. Heating is preferably to from50° to 100° C., in particular from 70° to 95° C. Gelling generallyoccurs in a time between 30 minutes and 2.5 hours. It is advantageous tothen allow the gels to mature for a further time, i.e. for example, tohold the gels at elevated temperature for a further period of from 10 to20 hours. The supply of heat for the gelling and optionally maturationcan, for example, occur in a circulated-air oven or by means ofmicrowaves or alternating fields. Even if the total treatment time isnot necessarily shorter than hitherto, the gel former does lose itsflowability in a shorter time.

Fire-resistant glass according to the invention contains fire-resistantgels according to the invention. Fire-resistant glass according to theinvention can be produced, for example, by allowing the above-describedgelling and optionally maturation of the gel formers according to theinvention to proceed between the panes of a composite pane consisting oftwo or more panes.

Gel formers according to the invention can be prepared, for example, byfirst reacting an aluminium compound capable of forming aluminiumphosphate, in particular aluminium hydroxide, and a phosphorus compoundcapable of forming aluminium phosphate, in particular orthophosphoricacid, in the desired atom ratio of aluminium to phosphorus in thepresence of water at, for example, from 70° to 120° C. to give analuminium phosphate solution. This solution can, for example, have asolids content of at least 40% by weight, preferably from 70 to 85% byweight. This solution is preferably allowed to stand for at least 4hours, better from 10 to 40 hours, at from 10° to 40° C. Separatelytherefrom, a boron compound capable of forming an alkanolamine salt, inparticular orthoboric acid, and an alkanolamine, in particularethanolamine, can then be combined in the desired ratio of boron atomsto alkanolamine molecules (e.g. 2 mol of alkanolamine per boron atom) inthe presence of water and the, preferably aged, aluminium phosphatesolution can then be added to this solution in the desired ratio.Moderate heating too, for example, from 50° to 85° C. then gives apreproduct of gel formers of the invention. After cooling to, forexample, below 45° C., this has a good shelf life and a low viscosity.

From the preproduct, gel formers according to the invention can beobtained by addition of alkali metal compounds in the above-describedmanner.

If the gel formation is carried out at temperatures above 100° C., itmay become necessary to carry out the gelling in a closed system. Thegel formation can be carried out directly with freshly prepared gelformer. However, it is preferable to store the gel former for at least24 hours at room temperature prior to gel formation.

The boron-alkanolamine solution can contain, for example, from 40 to100% by weight of solids and the aluminium phosphate solution ispreferably, optionally after appropriate dilution, likewise as asolution containing from 40 to 75% by weight of solids combined with theboron-alkanolamine solution.

The individual components can also be combined in a different manner,for instance when the preparation is to be carried out completely orpartially continuously and/or in a single-vessel process. For example,it is possible to first react the aluminium phosphate solution with thealkanolamine and then add the boron compound or first react the boronand/or phosphorus compound with an alkanolamine and then add, forexample, freshly precipitated aluminium hydroxide.

In place of the two-vessel process which is preferably used and in whichan aluminium phosphate solution and a boron-alkanolamine salt solutionare first prepared and the two solutions are then combined by stirringtogether or in a continuous mixing apparatus, it is also possible to usesingle-vessel processes.

In the preparation of the gel former, it is also possible to initiallyuse high solids concentrations and to then reduce these by dilutionbefore, during or after the preparation of the gel former.

If desired, it is also possible to add additives, for examplesurfactants, bonding agents, colorants, pore nucleus formers, fillers,light protection agents, antioxidants and/or reinforcers, to thestarting materials for preparing gel formers according to the inventionand/or to the gel formers according to the invention. Such additives areknown per se.

Get formers according to the invention have a good shelf life attemperatures of up to about 40° C. Fire-resistant gels according to theinvention are formed as clear, temperature-stable gels which arecharacterized by a good mechanical durability and, surprisingly, do nottend to flow at temperatures in the range from 100° to 600° C.

Unlike the previously known gel formers which contain no addition ofalkali metal compounds or amounts of alkali metal compounds smaller thanthose required according to the invention, gel formers according to theinvention gel, for example at 90° C., in less than 2 hours withouthaving an unsatisfactorily short shelf life at room temperature. Theshelf life at 20° C. is, for example, over 1 month, with the viscositiesremaining below those of the known gel formers having a comparablesolids content. The shorter gelling times have the advantage that theliquid gel former state which requires fixing of the composite panescontaining it lasts for only a short time.

As already stated, fire-resistant gels according to the invention donot, even at temperatures in the range from 100° to 300° C., tend toform a flowing melt which may be able to flow out of the cracks in thecovering glass panes which are unavoidably formed on the flame side whena flame is applied to fire-resistant composite glass. This is atechnically important, surprising advantage of the fire-resistant gelsof the invention.

Fire-resistant gels according to the invention have a fine-pored,moderate intumescence. The gel formers of the invention have relativelylow viscosities, even at solids concentrations of above 60% by weight.Even at dilutions to a solids content of less than 40% by weight theyare still capable of gelation and generally have somewhat more basic pHvalues than known gel formers, for example ones between 7 and 8.6.Fire-resistant gels according to the invention have a significantlyreduced crack-forming tendency and tend not to flow even at temperaturesup to 180° C., so that the hydrostatic pressure of the composite panescan be readily accommodated even in the case of relatively weak glasspanes. Besides the good storage stability at constant, even elevatedtemperatures, fire-resistant gels according to the invention also have agood thermal shock resistance, for example in the case of temperaturesfluctuating between -20°, +20° and +80° C. Finally, the high F and Gendurance times which the fire-resistant glass of the invention can haveare worthy of mention.

The fire-resistant glass of the invention can be produced by firstpreparing a gel former which is storage-stable at room temperature andwhich can then, after being placed between the glass panes, can beconverted into the stable gel in a short time by heating without furtheradditives. In the case of fire-resistant glass according to theinvention the intumescence of the gels in case of fire is not so high asto result in premature breaking of the fire-resistant glazing.

The sum of these advantages of the present invention represents aconsiderable technical advance in the field of fire protection.

In the preparation of fire-resistant gels according to the invention, itis also possible to use, if desired in addition to or in place of thepreferred aluminium hydroxide, other aluminium compounds which can beconverted into aluminium phosphates, for example aluminium oxides,hydrated aluminium oxides, aluminium salts of volatile acids (forinstance aluminium chloride, carbonates or acetates) and/or aluminiumborate.

In addition to or in place of the preferred orthophosphoric acid, it isalso possible to use, for example, other phosphorus compounds which canbe converted into aluminium phosphates, for example dehydrated forms oforthophosphoric acid, phosphorus oxides, phosphonic acids, phosphinicacids, phosphoric esters and/or salts of phosphoric acid, the latter,for example, as ammonium and/or alkanolamine salts.

In addition to or in place of the preferred orthoboric acid, it ispossible to use, if desired, other boron compounds, for exampledehydrated forms of orthoboric acid, boron oxides, ammonium boratesand/or alkanolamine borates.

In addition to or in place of the preferred ethanolamine, it is possibleto use, if desired, other alkoxylation products of ammonia such asdicthanolamine and/or triethanolamine.

Preferred alkali metal compounds are alkali metal hydroxides,particularly in the form of aqueous solutions. The alkali metal in thealkali metal compounds is preferably sodium. However, lithium, potassiumand higher alkali metals are also suitable. In addition to or in placeof the preferred alkali metal hydroxides, it is also possible to useother alkali metal compounds, for example oxides, carbonates,bicarbonates, formates, acetates, alkoxides, borates and/or aluminates.

Suitable glass for fire-resistant glass according to the invention maybe, for example, any inorganic or organic glass of the prior art.

The gel formers can, if desired, be diluted prior to gel formation. Thepreferred diluent is water, but an addition of organic solvents, atleast in part, is also possible, with the organic solvents preferablybeing miscible with water, but possibly also being immiscible withwater.

Apart from the above-mentioned additives, it is also possible to useadditions of carbonizing polyalcohols, for example sugars, glycols,glycerol, pentaerythritol and/or polyvinyl alcohols and otherwater-soluble oligomeric or polymeric additives. In specific cases, ifclear gel layers are not required, polymer dispersions and/or preferablysilica sols can also be mixed with fire-resistant gels or gel formersaccording to the invention. Bonding agents, surfactants,light-stabilizers, UV and IR filter substances and colouring additivesare optionally added in amounts of, for example, below 3% by weight,preferably below 1% by weight, based on the fire-resistant gel of theinvention. Fillers and carbonizing additives can optionally be used, forexample in amounts of from 1 to 75% by weight, preferably from 20 to 60%by weight, based on the total mixture.

It is extremely surprising that use of the amounts according to theinvention of alkali metal compounds changes the use properties of thegel formers, fire-resistant gels and fire-resistant glass in such anadvantageous manner, since smaller additions of alkali metal compoundsresult in occurrence of serious disadvantages in use, in particular apoorer ability to gel.

Gel formers according to the invention can also be used for producingauxiliaries, materials and components for preventive fire protection,for example by impregnating absorptive substrates, for instance powders,fibrous materials, foam materials, cellulose materials, papers,nonwovens, woven or knitted fabrics, with gel formers according to theinvention and then, optionally after shaping, carrying out the gelation.This gives, with or without partial or complete drying, materials whichhave a good fire-resistant action, intumescent character and are able tobe ceramicized. Thus, gel formers according to the invention can beused, for example, for producing protective housings for cables,flame-resistant wound coverings, fillings for hollow spaces, sealingelements and fire barriers.

Gel formers according to the invention can also be used as additives orformative components in the production of more flame-resistantpolyurethane foams.

Of interest in preventive fire protection or in the production ofmouldings or light materials is the combination of gel formers andfire-resistant gels according to the invention with expandablematerials, e.g. expandable silicates or graphites, in unexpanded,partially expanded or completely expanded form, for example by admixingsuch graphites and/or silicates with fire-resistant gels or gel formersaccording to the invention and optionally subjecting this mixture to ashaping process and/or a thermal post-treatment, e.g. between 80° and1000° C.

It is also possible to use fire-resistant gels according to theinvention in comminuted form or gel formers in spray-dried form or inthe form of material pulverized after drying, in massive form or (as aresult of its intumescent property) partially or completely thermallyexpanded form as insulating and fire-resistant hollow space filling, asfiller, as coating or pressed into plates or mouldings of another type,preferably for purposes of fire protection.

Since the gel formers of the invention have film-forming character, theyare suitable not only as impregnants, but also, in particular in thecase of water contents of from 10 to 50% by weight, as varnishes orcoatings on rigid or flexible substrates and give these, for instancemetals (such as aluminium), wood, woven fabrics, ceramics or plastics,an improved fire resistance.

The invention is illustrated below by way of example. Unless otherwiseindicated, parts and percentages are by weight.

EXAMPLES Example 1

Preparation of an alkali metal-free preproduct (not according to theinvention)

a) Preparation of an aluminium phosphate solution

3045 parts of technical-grade orthophosphoric acid (85% strength) wereheated with 726 parts of water to 80° C. 686.5 parts of aluminium oxidewere then added continuously over a period of 1 hour while stirring, themixture was stirred further for 45 minutes at 95° C. and was thencooled.

b) Preparation of an alkanolaminc borate solution

1600 parts of ethanolamine and 24 parts of water were stirred with 742parts of technical-grade orthoboric acid at 80° C. After 30 minutes, aclear solution had formed. The solution was then cooled to 40° C.

c) 4052 parts of solution prepared as described under a) were meteredcontinuously over a period of I hour into the solution freshly preparedas described under b) with good stirring. The mixture was then stirredfurther for 2 hours at 90° C. Add was then cooled over 30 minutes tobelow 40° C. The preproduct obtained (solution in water, pH: 6.4) wascolourless and clear and represented an aqueous solution having astrength of about 69%.

Example 2

Additions of alkali metal hydroxide to the preproduct obtained asdescribed in Example 1.

500 parts of the preproduct obtained as described in Example 1 were ineach case stirred with increasing amounts of 50% strength aqueous sodiumhydroxide solution at 40° C. (for details see Table 1).

The various preparations formed clear solutions. They were introducedinto test tubes in such a way that the tubes were filled to about 20% byvolume. The tubes were then laid at an angle in an oven (90° C.), leftthere for 24 hours and the time at which gelling commenced was observed(for details see Table 1).

The tubes were subsequently taken from the oven, stood vertically andtheir contents were assessed at room temperature (for details see Table1).

                  TABLE 1    ______________________________________    Addition of    aqueous NaOH Commencement                 atom    of gelling after                                   State after taking a                 ratio   (M = minutes,                                   sample from the    Sample          parts  Al:Na   H = hours)                                   oven and cooling    ______________________________________    A     --     --       6 H      clear, solid gel; crack-free    B     10     1:0.2   12 H      clear, solid gel; crack-free    C     20     1:0.4   31 H      clear, solid gel; crack-free    D     25     1:0.5   --        turbid liquid    E     30     1:0.6   --        turbid liquid    F     40     1:0.8   --        turbid liquid    G     30     1:1     --        clear liquid    H     60     1:1.2   --        clear, high-viscosity liquid    I     70     1:1.4    5 H      clear, solid gel, crack-free    K     75     1:1.5    2 H      clear, solid gel, crack-free    L     80     1:1.6   80 M      clear, solid gel, almost                                   crack-free    M     90     1:1.8   60 M      clear, solid gel; cracks    N     100    1:2.0   40 M      clear, solid gel; cracks    ______________________________________

The samples A and B correspond to the prior art, the samples C to H arefor comparative purposes and the samples I to N correspond tofire-resistant gels according to the invention.

Table 1 shows that good gels are obtained in accordance with the priorart after a relatively long time (samples A and B). With increasingadditions of sodium hydroxide solution, the gelling time then increasesgreatly (sample C), subsequently no gelling at all is obtained (samplesD to H). From sample I, gels then occur again, and these gel after avery short time.

The increase in the amount of alkali metal (atom ratio of aluminium toalkali metal of up to 1:1.2) thus first increasingly leads to unusableproducts. Completely surprisingly, even higher amounts of alkali metal(atom ratio of aluminium to alkali metal from 1:1.3) give propertieshaving very favourable use properties.

Example 3

The melting resistance at from 160° to 165° C. of gels obtained asdescribed in Example 2 was tested as follows:

A sample of the respective gel was introduced into a test tube in such away that it adhered to the wall of the test tube when this was stoodvertically and the bottom of the test tube was partly free. The testtubes were then, in a vertical position, exposed for 5 minutes to astream of air at 165° C. Gels which melted collected in a readilyvisible manner at the bottom of the test tube.

A test temperature of from 160° to 165° C. was selected because in thetesting of fire-resistant glass in a furnace in accordance with DIN 4112the side of the test pane facing away from the flame should not becomehotter than 160° C. The gel should thus as far as possible not melt awayat 160° C.

The test results are shown in Table 2.

                  TABLE 2    ______________________________________    Sample          Observation    ______________________________________    A     moderate, but distinct melting and flowing away of the gel    B     somewhat less flowing away of the gel than in the case of A    C     significantly greater melting away than in the case of A    I     significantly less and more viscous flowing away than in the          case of A    K     no melting away, but only softening of the gel    L     no melting away, only slight softening of the gel    M     no melting away, no softening of the gel observed    N     gel cracks without melting    ______________________________________

The samples A and B correspond to the prior art, sample C is forcomparative purposes, the samples I to N correspond to fire-resistantgels according to the invention.

Looking at Tables 1 and 2 together, it can be seen that short gellingtimes together with a low melting tendency at 160° to 165° C. isachieved only by fire-resistant gels having a composition according tothe invention.

Example 4

Samples A and I to N obtained as described in Example 2 were each heatedto 500° C. in test tubes. All samples gave fine-pored intumescencefoams. The samples I to N foamed less strongly than the sample A.

Example 5

Fire-resistant glass according to the invention and comparative testingin the fire test

Three-pane composites sealed with silicone sealant and having thedimensions 50×50×1.5 cm were produced and fixed vertically between twosteel plates. The structure of the composite was: 3 mm float glass/3 mmintermediate space/3 mm float glass/3 mm intermediate space/3 mm floatglass.

a) The intermediate spaces of the composite were filled with the gelformer corresponding to the sample A from Example 2 prior to gelation(comparative experiment).

b) The intermediate spaces of a second composite were filled with thegel former corresponding to the sample L from Example 2 prior to gelformation (according to the invention).

Both composites were, in fixed form, introduced horizontally into anoven and heated for 20 hours at 90° C. They were then allowed to coolover a period of 10 hours. The fire-resistant glass thus produced wasclear and transparent. Owing to the mechanically stable gel formed italso did not tend to deform as a result of hydrostatic pressure of thefillings.

A 50-cycle alternating temperature storage test (10 hours at each of-10° C., room temperature and +80° C.) showed no deterioration of theglass composites.

Comparison

The two composites 5a) and 5b) were, after storage for 2 months at roomtemperature, installed in a small-fire furnace operated in accordancewith DIN 4102 using the standard temperature curve. The flame test wasthen commenced. In both cases, the glass pane facing the flame crackedafter from 1 to 2 minutes. After about 3 minutes opacification of thepane could be clearly seen in each case. After 26 minutes, melting awayand the formation of floating bubbles could be seen in the lower regionof the pane on the side facing away from the flame in the case of 5a),after 41 minutes the contents of the lower intermediate space facingaway from the flame had partly run out but it began to partly refill asa result of intumescent foaming of the filling. The average temperatureof the composite 5a) reached values of above 180° C. after 44 minutes.

In the case of composite 5b), increasingly fine bubbles appeared in thegel layer after 5 minutes, without noticeable flowing or running-outprocesses, the bubbles increasingly assuming the character of afine-pored foam over the entire test time. From a test time of about 18minutes, this foaming process also occurred in the second gel layer.Even after from 25 to 30 minutes burning time no pronounced heat spotscould be scen on the surface of the pane. After 53 minutes, the outersurface of the pane reached an average temperature of 180° C. Thecomposite 5b) was now filled with a fine-pored foam in the manner of acushion.

After 120 minutes burning time, both composite panes still representedcomplete closure of a space. The test was then stopped and the frontfacing the flame was assessed after cooling.

In the case of 5a), it was found that certain amounts of the originalgel filling had sunk downwards out of the broken panes and had vitrifiedthere. On the intact parts of the glass panes, the remaining layer ofthe readily wetting glass melt had expanded with ceramicization to givea foam material.

In the case of 5b), it was found that almost no material had sunk downor run out into the fire space and that the entire surface facing theflame represented a type of fine-pored foam cushion of ceramicizedmaterial. This enables the closure of a space to be maintained over along time.

These fire tests show the significantly improved suitability of the gels5b) according to the invention for fire-resistant intermediate gellayers in fire-resistant glass.

What is claimed is:
 1. A fire-resistant glass which contains afire-resistant gel, said fire-resistant gel being a gelled form of a gelformer containing a) an acid aluminum phosphate and b) a reactionproduct of boric acid with an alkanolamine, in which a) and b),calculated as solids, are present in a weight ratio of from 100:95 to100:0.5 wherein the said gel former additionally contains one or morealkali metal compounds in an atomic ratio of aluminum to alkali metal of1:1.3-2.5.
 2. Process for producing a fire-resistant glass whichcomprises forming a gel former bya) reacting an aluminum compoundcapable of forming aluminum phosphate and a phosphorus compound capableof forming aluminum phosphate in the presence of water at a temperatureof from 70° to 120° C. to form an aluminum phosphate solution having asolids content of at least 40% by weight, allowing this solution tostand for at least 4 hours at from 10° to 40° C., b) combining a boroncompound capable of forming an alkanolamine salt and an alkanolamine inthe presence of water, to form a solution, c) mixing the solution formedin step a) with the solution formed in step b) in a weight ratio ofa):b), calculated as solids, of from 100:95 to 100:0.5, and heating toform a preproduct, then d) adding to the preproduct of c) an alkalimetal compound in the form of a 50% to 70% strength by weight solutionin an amount sufficient to form a product having an atomic ratio ofaluminum to alkali metal of 1:1.3-2.5, at a temperature of from 10° to100° C. to form the gel former, andplacing the gel former thus formedbetween two panes of glass and heating the glass for from 30 minutes to2.5 hours to maintain the temperature of the gel former at from 50° to120° C., thereby to convert the gel former to a gel.